Heat exchanger

ABSTRACT

A heat exchange device ( 1 ), e.g., for a syngas reactor, comprising a channel wall ( 3 ) defining a flow channel and one or more heat exchange surfaces ( 5   a - d ), each embedding one or more flow paths for a fluid heat exchange medium. A support structure ( 20 ) supports the heat exchange surfaces ( 5   a - d ) within the flow channel. The support structure ( 20 ) comprises a plurality of arms ( 21 ) extending from a central crossing ( 22 ) to the channel wall ( 3 ). The arms ( 21 ) of the support structure can embed evenly distributed, e.g., meandering inner channels ( 23 ) which can be in open connection with the flow paths in the heat exchange surfaces ( 5   a - d ).

The present invention relates to a heat exchange device for cooling a gas, comprising a channel and one or more heat exchange surfaces disposed in the channel, supported by a support structure.

Such heat exchangers are for example used in gasification processes for the production of synthetic gas, or syngas. In such a process, carbonaceous feedstock is partially oxidised in a reactor. Syngas leaving the reactor typically has a temperature of 1300-1600° C. The hot syngas is quenched to temperatures between 100-700° C. and is then transported to a coiled heat exchanger, generally comprising a number of parallel coiled tubes.

Support structures are used to support the heat exchange surfaces within the channel formed by the channel wall. Differences in thermal expansion of the various parts complicate possible support constructions. Sliding bearings can be used, allowing some degree of freedom of movement, but such bearings are difficult to realize and less reliable under the circumstances in such reactors.

U.S. Pat. No. 5,482,110 discloses a heat exchanger for cooling syngas from a partial combustion reactor comprising nested heat exchange surfaces carried by a support. Such a support structure may induce high local stress peaks.

It is an object of the present invention to provide a heat exchanger device with a robust support structure enabling reduction of loads caused by differences in thermal expansion by the various parts.

The object of the invention is achieved by a heat exchange device comprising:

-   a channel wall defining a flow channel; -   one or more heat exchange surfaces within the flow channel, each     heat exchange surface embedding one or more flow paths for a fluid     heat exchange medium, and comprising supply and discharge     connections for the supply and discharge of the fluid heat exchange     medium; -   a support structure for supporting the heat exchange surfaces;     wherein the support structure comprises a plurality of arms     extending from a central crossing to the channel wall.

The heat exchange surfaces can rest on the support structure, or the heat exchange surfaces can hang down from the support structure. The one or more heat exchange surfaces can be connected to the support structure, e.g., by welding joints. The support structure can be joined to the channel wall, or to a load bearing structure within the channel wall.

The device can for instance have a number of nested heat exchange surfaces of a closed geometry, e.g., of a cylindrical geometry, as is disclosed in U.S. Pat. No. 5,482,110. The heat exchange surfaces can be coaxially arranged or nested within the channel wall, which will typically be cylindrical. Optionally, the support structure can support a series of two or more bundles of nested heat exchange surfaces.

Generally, the fluid heat exchange medium is water, although any other type of aqueous or non-aqueous coolant can be used if so desired.

The support structure may for example have three or more arms, e.g., four or more arms to form a cross. If so desired a higher number of arms can be used.

The support structure can comprise a plurality of embedded parallel inner channels each being in open connection with one of the flow paths in the heat exchange surfaces. To equalize thermal expansion, the inner channels are preferably evenly distributed and equidistantly arranged. To this end, the inner channels may meander through the arm parts of the support structure. Since meandering inner channels are difficult to manufacture, the arm parts may be built of a number of sections each embedding parallel and equidistant inner channels making a single turn, e.g., of about 90 degrees. For example, each arm of the support structure may comprise:

-   a first lower arm part with equidistantly arranged parallel flow     paths with a first part extending upwardly to a first corner and a     second section extending from the first corner in the direction of     the crossing section; -   a second lower arm part with equidistantly arranged parallel flow     paths having a first section in line with the second section of the     respective flow paths in the first part extending to a second     corner, and a second section extending upwardly from the second     corner; -   an upper arm part with equidistantly arranged parallel flow paths     having a first vertical section in line with the second section of     the respective flow paths in the second lower arm part and extending     upwardly to a third corner, and a horizontal second section     extending from the third corner away from the crossing section.

The heat distribution with this configuration is such that differences in thermal expansion of the connected parts do not result in high mechanical stress loads.

The arms of the support structure can for example be formed as blocks or plates embedding inner channels operatively connected to the tubular parts. Alternatively, one or more of the arms of the support structure can wholly or partly be composed of tubular parts, optionally in combination with blocks or plates embedding inner channels operatively connected to the tubular parts.

If a larger number of heat exchange surfaces, or heat exchange surfaces of a higher weight, are to be supported, the height of the support structure can be increased. This way, the support structure can be made stronger without increasing the thickness of the support structure arms, which could result in undesirable high wall temperatures of the support structure.

The thickness of the arms of the support structure should be sufficient to give the support structure the required carrying capacity. Generally, a wall thickness of 5-20 mm at both sides of an inner channel balances sufficient strength with good heat dissipation capacity.

Particularly for the cooling of deposit-forming gases from pressure-loaded pyrolysis and gasification reactors it is desirable that the heat exchange surfaces are cleaned by rapping devices which can regularly be actuated during operation of the reactor. With the aid of, e.g., pneumatically operated rapping devices the individual heat exchange surfaces are accelerated to such an extent, that soot deposits and fouling are effectively removed. Cleaning by rapping can be done particularly effectively if all tubes of one heat exchange surface unit are rigidly connected to one constructive gastight unit, e.g., by constructing the heat exchange surfaces as a tube-stay-tube or fin-tube construction.

The heat exchange surfaces can be assembled as a plurality of nested heat exchange surfaces of a closed geometry whereby the inner heat exchange surface has a greater constructive height than the adjacent outer heat exchange surface so that each heat exchange surface can be rapped from the exterior without the need for penetrating any other heat exchange surfaces. Optionally, one or more deflectors arranged within the inner heat exchange surface of the nested set may be used to guide the hot gas flow towards the heat exchange surfaces, in order to cool all of the gas evenly.

The heat exchange device according to the present invention can for example be a section of a partial combustion reactor for the production of synthetic gas.

The invention is further explained under reference to the accompanying drawings. In the drawings:

FIG. 1A: shows a longitudinal cross section of a heat exchange device according to the present invention;

FIG. 1B: shows the device of FIG. 1A in cross section;

FIG. 2A: shows in side view a support structure of the device of FIG. 1;

FIG. 2B: shows a plan view of the support structure of FIG. 2A;

FIG. 3: shows in side view of a second possible embodiment of a support structure according to the invention;

FIG. 4: shows a longitudinal cross section of a further possible embodiment of a heat exchange device according to the present invention.

FIG. 1A shows in longitudinal cross section a heat exchange section 1 of a partial combustion reactor for the production of syngas. The section 1 comprises a cylindrical outer wall 2. The outer wall 2 encloses a concentrically arranged inner channel wall or membrane 3 built of parallel tubular pipe lines, schematically represented in the drawing by centrelines. The tubular pipe lines of the inner channel wall 3 are welded together—e.g., directly or via fins—to form a gastight wall. A cooling medium, such as water flows through the pipe lines of the channel wall 3.

The inner channel wall 3 encloses a set of four schematically represented nested coaxial heat exchange surfaces 5 a, 5 b, 5 c, and 5 d. In practice, two or more may be used—for example heat exchange surfaces 5 a and 5 b. Like the inner channel wall 3, the heat exchange surfaces 5 a-d are built of parallel tubular lines. Optionally, the tubular lines of the heat exchange surfaces 5 a-d can be helically wound.

The inner channel wall or membrane 3 defines a central channel 4 a for hot gas flowing downwards along the heat exchange surfaces 5 a-d towards a discharge. At the lower end of the inner channel wall 3, the cooled gas can enter the annular space 4 b between the inner channel wall 3 and the outer wall 2. Coolant flowing through the pipe lines of inner channel wall 3 isolates the cool gas in the annular channel 4 b from the hot gas in the central channel 4 a.

The lower end 6 of each inner heat exchange surface 5 b-d extends past the lower end 6 of the adjacent outer heat exchange surface 5 a-c, respectively. This way, each individual heat exchange surface 5 a-d can be cleaned individually by using rapper devices (not shown).

Four or more equidistantly arranged coolant discharge lines 7 are provided between the inner channel wall 3 and the outer channel wall 2, as schematically shown in FIG. 1B. Referring back to FIG. 1A, the discharge end 8 of the lines 7 passes the outer wall 2 to form a connection to a coolant discharge. In line with the discharge lines 7, and at a distance below these discharge lines 7, are four supply lines 9. The upper ends 10 of the supply lines 9 pass through the outer wall 2 to form a connection to a coolant supply. Coolant feed lines 16 connect the supply lines 9 to the heat exchange surfaces 5 a-d. The arrangement of the supply lines and discharge lines can also be reversed depending on the cooling media.

A horizontal support cross 20 has four arms 21 extending from a central crossing 22 to a corresponding coolant discharge line 7. The support cross 20 is shown in more detail in FIGS. 2A and 2B. Parallel inner channels 23 run through the arms 21, each inner channel 23 being in open connection with the flow paths in the heat exchange surfaces 5 a-d. The inner channels 23 are evenly distributed over the corresponding arm 21. The top side of each of the heat exchange surfaces 5 a-d comprises two vertical line sections 19, axially symmetrically arranged, extending vertically towards the support cross 20, where they are connected to the embedded inner channels 23, as shown in FIG. 1A.

Each arm 21 comprises a first and a second lower arm part 24, 25 respectively, and an upper arm part 26. In the first lower arm part 24, equidistantly arranged parallel flow paths 27 have a first part 27 a extending upwardly to a first corner 27 b and a second section 27 c extending in the direction of the crossing section 22.

In the second lower arm part 25 are embedded equidistantly arranged parallel flow paths 28. Two of the four second lower arm parts 25 form a single block, while the other two are formed as separate parts at opposite sides of the block and under right angles with it and are welded to a central section of the block to form a cross, as shown in FIG. 2B. Referring back to FIG. 2A, the flow paths 28 in the second lower arm parts 25 have a first horizontal section 28 a in line with the respective flow paths 27 c in the first part 24 extending to a second corner 28 b, and a second section 28 c extending upwardly from the second corner 28 b.

In the upper arm part 26 are embedded equidistantly arranged parallel flow paths 29. Two of the four upper arm parts 26 form a block, while the other two upper arm parts 26 are formed as separate parts and are welded to the central section of the block to form a cross. The flow paths 29 in the upper arm parts 26 have a first vertical section 29 a in line with the respective flow paths 28 in the second lower arm part 25 extending upwardly to a third corner 29 b, and a second section 29 c extending from the third corner 29 b away from the crossing section 22.

Opposite to the side forming the crossing section 22, the upper arm parts 26 are joined to an extension part 30. These extension parts 30 are rectangular parts with equidistantly arranged inner channels 31 embedded in line with the horizontal channel sections 28 c in the upper arm parts 26.

In this configuration, all parts of the support cross 20 are evenly cooled by the evenly distributed inner channels 27, 28, 29, 31 in arm parts 24, 25, 26, 30. As a result, the risk of mechanical stresses induced by differences in thermal expansion is substantially reduced.

The outer ends of inner channels 27, 28, 29, 31 in arm parts 24, 25, 26, 30 are surrounded by circular rims 35. The arm parts 24, 25, 26, 30 are welded together at these circular rims to form leaktight joints.

Blocks 32 (see FIG. 2B) are attached to both sides of the extension part 30. The blocks 32 are in line with the inner channel wall 3 and have the same curvature. The blocks 32 are provided with inner channels 33 which are operatively connected to the tubular lines 4 in the channel wall 3.

FIG. 3 shows in side view an alternative support cross 40 for a heat exchanger according to the present invention. The support cross comprises four arms 41 of equal length forming a cross with a centre part 42. Each arm 41 is made of four sections: a lower main section 43, a lower central section 44, an upper centre section 45 and an upper main section 46. Inner channels 47 a and 47 b are embedded in the lower main section 43 with a vertically extending channel section 47 a at the lower side of the lower main section 43 and a horizontally extending channel section 47 b, extending to a lateral side of the lower main section 43. Three of the channel sections 47 b extend towards the adjacent lower central section 44. The upper one of channels sections 47 b has its upper longitudinal half formed as a pipeline in a rectangular cut-out 48 in the lower main section 43.

Inner channels 49 a and 49 b are embedded in the lower central section 44, having horizontal channel sections 49 a connected at one end to the channel sections 47 b in the lower main section 43, and to vertical channel sections 49 b at their other end. The lower central section 44 is mirrored by the upper central section 45, which embeds inner channels 50 a and 50 b, with vertical sections 50 a in line with the vertical inner channels sections 49 b in lower central section 44. Horizontal channels sections 50 b lead from the vertical channel sections 50 a to the side of the upper central section 45 opposite the centre 22.

The upper main section 46 is made of three horizontal parallel pipe lines 51 operatively connected to the horizontal channel sections 50 b in upper central section 45. The pipe lines 51 lead to an extension block 52 with three inner channels 53 connected to the pipe lines 51.

The outer ends of inner channels in arm parts 43, 44, 45 and the pipe lines 51 of upper main section 46 are surrounded by circular rims 54. The arm parts are welded together at these circular rims 54 to form leaktight joints.

FIG. 4 shows a heat exchange device 60 similar to the heat exchange device of FIGS. 1A and 1B. The same reference numbers are used for parts that are the same in both embodiments. The heat exchange device in FIG. 4 comprises two bundles 61, 62 in line above one another of four nested heat exchange surfaces 61 a-d, 62 a-d. Because of the double weight that has to be supported a support cross 63 is used which is thicker than the support cross 20 in FIG. 1A. 

1. A heat exchange device comprising: a channel wall defining a flow channel; one or more heat exchange surfaces, each embedding one or more flow paths for a fluid heat exchange medium, and comprising supply and discharge connections for the supply and discharge of the fluid heat exchange medium; and a support structure for supporting the heat exchange surfaces within the flow channel; wherein the support structure comprises a plurality of arms extending from a central crossing to the channel wall; and wherein at least a part of the arms comprises inner channels each being in open connection with one of the flow paths in the heat exchange surfaces.
 2. A heat exchange device according to claim 1 wherein the inner channels are parallel and equidistant and evenly distributed over the corresponding arm.
 3. A heat exchange device according to claim 2 wherein the inner channels meander through the arms.
 4. A heat exchange device according to claim 3 wherein the arms are built of two or more arm parts, wherein at least a part of the arm parts embed parallel and equidistant inner channel sections making a single turn.
 5. A heat exchange device according to claim 4 wherein each arm comprises: a first lower arm part with equidistantly arranged parallel flow paths with a first section extending upwardly to a first corner and a second section extending in the direction of the crossing section; a second lower arm part with equidistantly arranged parallel flow paths having a first section in line with the second sections of the respective flow paths in the first lower arm part, wherein the first sections extend to a second corner, and second section extend upwardly from the second corner; and an upper arm part with equidistantly arranged parallel flow paths having a first vertical section in line with the second sections of the respective flow paths in the second lower arm parts, wherein the first sections extending upwardly to a third corner, and wherein second sections extend from the third corner away from the crossing section.
 6. A heat exchange device according to claim 1 wherein the device comprises two or more coaxially nested heat exchange surfaces of a closed geometry.
 7. A heat exchange device according to claim 1, wherein the support structure comprises four arms under right angles forming a cross.
 8. A heat exchange device according to claim 1 wherein one or more of the arms of the support structure is at least partly built of tubular parts, optionally in combination with blocks or plates embedding inner channels operatively connected to the tubular parts.
 9. A partial combustion reactor for the production of synthetic gas, wherein the reactor comprises at least one section with a heat exchange device according to claim
 1. 